[PATCH 4/4] i2c: i2c-stm32f7: add PM_SLEEP suspend/resume support

[Alain Volmat <alain.volmat@xxxxxx>]

Backup/restore I2C registers as part of the suspend/resume
handlers. The device is marked as suspended to ensure that
transfers are rejected during the suspended period.

Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@xxxxxx>
Signed-off-by: Alain Volmat <alain.volmat@xxxxxx>
---
 drivers/i2c/busses/i2c-stm32f7.c | 118 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 114 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index b2634afe066d..75a3e8107a60 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -169,6 +169,24 @@
 #define STM32F7_AUTOSUSPEND_DELAY		(HZ / 100)
 
 /**
+ * struct stm32f7_i2c_regs - i2c f7 registers backup
+ * @cr1: Control register 1
+ * @cr2: Control register 2
+ * @oar1: Own address 1 register
+ * @oar2: Own address 2 register
+ * @pecr: PEC register
+ * @tmgr: Timing register
+ */
+struct stm32f7_i2c_regs {
+	u32 cr1;
+	u32 cr2;
+	u32 oar1;
+	u32 oar2;
+	u32 pecr;
+	u32 tmgr;
+};
+
+/**
  * struct stm32f7_i2c_spec - private i2c specification timing
  * @rate: I2C bus speed (Hz)
  * @rate_min: 80% of I2C bus speed (Hz)
@@ -298,6 +316,7 @@ struct stm32f7_i2c_dev {
 	struct stm32f7_i2c_timings timing;
 	struct i2c_client *slave[STM32F7_I2C_MAX_SLAVE];
 	struct i2c_client *slave_running;
+	struct stm32f7_i2c_regs regs;
 	u32 slave_dir;
 	bool master_mode;
 	struct stm32_i2c_dma *dma;
@@ -2027,8 +2046,7 @@ static int stm32f7_i2c_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM
-static int stm32f7_i2c_runtime_suspend(struct device *dev)
+static int __maybe_unused stm32f7_i2c_runtime_suspend(struct device *dev)
 {
 	struct stm32f7_i2c_dev *i2c_dev = dev_get_drvdata(dev);
 
@@ -2038,7 +2056,7 @@ static int stm32f7_i2c_runtime_suspend(struct device *dev)
 	return 0;
 }
 
-static int stm32f7_i2c_runtime_resume(struct device *dev)
+static int __maybe_unused stm32f7_i2c_runtime_resume(struct device *dev)
 {
 	struct stm32f7_i2c_dev *i2c_dev = dev_get_drvdata(dev);
 	int ret;
@@ -2053,11 +2071,103 @@ static int stm32f7_i2c_runtime_resume(struct device *dev)
 
 	return 0;
 }
-#endif
+
+static int __maybe_unused
+stm32f7_i2c_regs_backup(struct stm32f7_i2c_dev *i2c_dev)
+{
+	int ret;
+
+	ret = pm_runtime_get_sync(i2c_dev->dev);
+	if (ret < 0)
+		return ret;
+
+	i2c_dev->regs.cr1 = readl_relaxed(i2c_dev->base + STM32F7_I2C_CR1);
+	i2c_dev->regs.cr2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_CR2);
+	i2c_dev->regs.oar1 = readl_relaxed(i2c_dev->base + STM32F7_I2C_OAR1);
+	i2c_dev->regs.oar2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_OAR2);
+	i2c_dev->regs.pecr = readl_relaxed(i2c_dev->base + STM32F7_I2C_PECR);
+	i2c_dev->regs.tmgr = readl_relaxed(i2c_dev->base + STM32F7_I2C_TIMINGR);
+
+	pm_runtime_put_sync(i2c_dev->dev);
+
+	return ret;
+}
+
+static int __maybe_unused
+stm32f7_i2c_regs_restore(struct stm32f7_i2c_dev *i2c_dev)
+{
+	u32 cr1;
+	int ret;
+
+	ret = pm_runtime_get_sync(i2c_dev->dev);
+	if (ret < 0)
+		return ret;
+
+	cr1 = readl_relaxed(i2c_dev->base + STM32F7_I2C_CR1);
+	if (cr1 & STM32F7_I2C_CR1_PE)
+		stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1,
+				     STM32F7_I2C_CR1_PE);
+
+	writel_relaxed(i2c_dev->regs.tmgr, i2c_dev->base + STM32F7_I2C_TIMINGR);
+	writel_relaxed(i2c_dev->regs.cr1 & ~STM32F7_I2C_CR1_PE,
+		       i2c_dev->base + STM32F7_I2C_CR1);
+	if (i2c_dev->regs.cr1 & STM32F7_I2C_CR1_PE)
+		stm32f7_i2c_set_bits(i2c_dev->base + STM32F7_I2C_CR1,
+				     STM32F7_I2C_CR1_PE);
+	writel_relaxed(i2c_dev->regs.cr2, i2c_dev->base + STM32F7_I2C_CR2);
+	writel_relaxed(i2c_dev->regs.oar1, i2c_dev->base + STM32F7_I2C_OAR1);
+	writel_relaxed(i2c_dev->regs.oar2, i2c_dev->base + STM32F7_I2C_OAR2);
+	writel_relaxed(i2c_dev->regs.pecr, i2c_dev->base + STM32F7_I2C_PECR);
+
+	pm_runtime_put_sync(i2c_dev->dev);
+
+	return ret;
+}
+
+static int __maybe_unused stm32f7_i2c_suspend(struct device *dev)
+{
+	struct stm32f7_i2c_dev *i2c_dev = dev_get_drvdata(dev);
+	int ret;
+
+	i2c_mark_adapter_suspended(&i2c_dev->adap);
+	ret = stm32f7_i2c_regs_backup(i2c_dev);
+	if (ret < 0) {
+		i2c_mark_adapter_resumed(&i2c_dev->adap);
+		return ret;
+	}
+
+	if (!stm32f7_i2c_is_slave_registered(i2c_dev)) {
+		pinctrl_pm_select_sleep_state(dev);
+		pm_runtime_force_suspend(dev);
+	}
+
+	return 0;
+}
+
+static int __maybe_unused stm32f7_i2c_resume(struct device *dev)
+{
+	struct stm32f7_i2c_dev *i2c_dev = dev_get_drvdata(dev);
+	int ret;
+
+	if (!stm32f7_i2c_is_slave_registered(i2c_dev)) {
+		ret = pm_runtime_force_resume(dev);
+		if (ret < 0)
+			return ret;
+		pinctrl_pm_select_default_state(dev);
+	}
+
+	ret = stm32f7_i2c_regs_restore(i2c_dev);
+	if (ret < 0)
+		return ret;
+	i2c_mark_adapter_resumed(&i2c_dev->adap);
+
+	return 0;
+}
 
 static const struct dev_pm_ops stm32f7_i2c_pm_ops = {
 	SET_RUNTIME_PM_OPS(stm32f7_i2c_runtime_suspend,
 			   stm32f7_i2c_runtime_resume, NULL)
+	SET_SYSTEM_SLEEP_PM_OPS(stm32f7_i2c_suspend, stm32f7_i2c_resume)
 };
 
 static const struct of_device_id stm32f7_i2c_match[] = {
-- 
2.7.4